If you visited the Khyber Pass without incident then congratulations you are brave! Most people buy the Afghan notes on the Afghan border but I didnt do that because they were asking too much and I was on a budget. I stopped off in the bazaar area of Landi Kotal and picked up some interesting old notes from Afghanistan. If you want true old currency at a cheap price then stop in Landi for a few moments and haggle for half a dozen notes. My notes are older and have more character than the ones the teens were offering on the border.